A liquid crystal display (LCD; liquid crystal display device), which displays images via a liquid crystal panel, has mainly two basic functions. One of them is to illuminate the liquid crystal panel from its back surface (lighting function), and the other function is to control the light to be displayed by the liquid crystal panel (display control function).
According to recent ever-increasing user needs, a casing trim of the liquid crystal panel (frame part which surrounds an image display region) needs to be narrowed down by improving the lighting function so that the light is extensively illuminated. The needs must be satisfied while securing display quality.
A document 1, which will be described later, discloses a practical technique which makes a breakthrough for narrowing the casing trim of a liquid crystal panel such as the above liquid crystal panel. FIG. 9 is an explanatory diagram (principle cross sectional diagram) showing a liquid crystal display disclosed in the document 1. As shown in FIG. 9, the liquid crystal display includes a liquid crystal panel 101, and a lighting section 102 including a fluorescent tube L for lighting (illuminating) and a light guide body 106.
In order to narrow the casing trim, in the liquid crystal display, cutouts are provided at both ends of the light guide body (transparent resin) 106 in the lighting section 102, and the fluorescent tube L is provided in the cutouts. That is, according to the liquid crystal display, part of the fluorescent tube L is provided within an effective display region (inside dotted lines V).
In addition, in this technique, in order to uniformize luminance (brightness) of the lighting, a scatterer 105, provided on top of the fluorescent tube L, is used along with the light guide body 106. The scatterer 105 is made of a resin including light scattering agent. Addition density of the scattering agent in the scattering body 105 is optimized in accordance with a haze of a diffusion sheet covering the upper part of the scatterer 105. This secures the uniformity of the luminance in the entire display region of the liquid crystal panel 101.
Note that, in the above arrangement, the light from the fluorescent tube is guided to the entire display region by the light guide body (normally a flat plate shape) provided adjacent to the fluorescent tube.
According to the light guide body, if the light, which goes into the light guide body from the fluorescent tube, has total reflection in an upper surface (a surface on a side of the liquid crystal panel side) or in a back surface, then it is not possible to uniformize the luminance. This is because the display light (i.e., the light to be displayed by the liquid crystal panel) of a reflected portion decreases. In view of the circumstances, a pear-skin texture (emboss) is formed on the upper and back surfaces of the light guide body to scatter the light.
Such a pear-skin texture is disclosed in the document 1 and a document 2 which will be described later. The document 2 discloses a technique in which a plurality of dotted-like pear-skin texture regions (pear-skin texture dots) are formed on the back surface of the light guide body. In this technique, the pear-skin texture dots are small in a part in the vicinity of the fluorescent tube (fluorescent tube vicinal part), whereas the pear-skin texture dots are large in a portion farther from the fluorescent tube. With this arrangement, light scattering quantity in the portion in the vicinity of the fluorescent tube (portion which receives a large amount of light) is less than that in the portion, farther from the fluorescent tube, which receives a small amount of light. As a result, the luminance of the display region is uniformized.
[Document 1] Japanese unexamined patent publication No. 235805/2000 (Tokukai 2000-235805, published on Aug. 29, 2000). Corresponding U.S. Pat. No. 6,412,969B1.
[Document 2] Japanese unexamined patent publication No. 313883/1994 (Tokukaihei 6-313883, published on Nov. 8, 1994). Corresponding U.S. Pat. No. 5,394,308.
However, in the case where the luminance is uniformized by changing the pear-skin texture dot size as described in the document 2, many regions having no pear-skin texture (regions between the dots) are formed on the back surface of the light guide body. As such, the absolute quantity of the light scattering cannot be increased. Here, such a problem arises that cannot increase the overall luminance.
Alternatively, it may be possible to form plural kinds of the pear-skin texture regions, whose densities (degree of scattering) are different from each other, on the entire back surface of the light guide body. However, it is technically difficult to form extremely low-density pear-skin texture. Therefore, in this case, it is impossible to sufficiently reduce the light scattering quantity. This gives rise to the excessively increase of the luminance of this portion, thereby resulting in that it is impossible to uniformize the luminance.